Recent published work by the author and co-workers has cast doubt on the generally accepted picture of the electronic structure and excited state order of the linear polyenes including the visual chromophore retinal and its derivatives. This new work indicates that the lowest excited singlet state of the linear polyenes has 1Ag symmetry in the idealized C2h point group in contrast to previous theoretical and experimental work which assumed that the easily observed transiton to the 1Bu state was to the lowest excited singlet. The proposed work is intended to confirm this new excited state order for linear polyenes in general with particular emphasis on compounds closely related to the visual pigments and to determine the properties of this excited state including vibronic mixing between one 1Ag and 1Bu states, radiative and radiationless lifetimes, conformational distortions in the excited state as deduced from a vibrational analysis and the effects of substitution of one of the carbon atoms by oxygen or nitrogen. The major activity will be high resolution, low temperature mixed crystal spectroscopy since this is the only unambiguous technique for determining excited state order in these compounds. A wide variety of promising mixed crystal systems will be tried. Fluorescence lifetimes and quantum yields will be determined since the presence of a low lying 1Ag state results in an abnormally long fluorescence lifetime. Two-photon spectroscopy, resonance Raman scattering and manetic circular dichroism will also be investigated.